There are about five to six million semi-trailers in use in the U.S., and a similar number of Class 5, 6, and 7 straight rail medium and heavy trucks, and class 8 tractors. These tractors, trucks and trailers are produced by several domestic and foreign truck manufacturers, and each manufacturer typically offers multiple models and styles. Despite the large number of tractors and trucks in use and the wide variety of models and styles available, virtually all of the trailers and most of the trucks have an elevated bed that can be difficult to access. As a result, falls from cabs, trailers, and 5th-wheel “catwalks” are the leading cause of insurance claims in the commercial trucking industry. Such falls can cause severe and debilitating injury, and even death.
A typical trailer floor is 48″ above the ground, often with only the 24″ under-ride guard beam mandated by the Interstate Commerce Commission (ICC beam) to assist in the climb, making access to the cargo bay difficult. The ICC beam is required to be located at the back of trailers to prevent the front end of a car, crashing into the rear end of a trailer, from passing under the trailer floor, and shearing off the passenger compartment at about shoulder level. This beam, usually a very robust 4″×4″ steel box section, often spans the full 102″ width of the rear trailer, and is suspended from below the trailer floor by, usually two, comparably robust, vertical steel supports. A car impacting the ICC beam would dissipate energy through bending of the ICC beam support structure, and would activate seat-belt-locks, air-bags, and other energy-dissipating features of the car—giving car passengers the best chance for survival.
The ICC beam's height has been standardized at about 24″ above ground, with its rear face roughly in-plane with the other features of the trailer's rear structure. The aft edge of the cargo floor, and the aft face of the cargo door, are set about 2″ forward of the ICC beam, to avoid contact during a typical cargo-dock bump. The ICC beam serves as a positive stop when backing into some dock walls. Other docks may have a mechanical “catcher” that firmly clamps the beam at its center during load/unload to maintain tight contact between the trailer and the dock.
When the cargo bay must be accessed in the absence of a dock, the upper surface of the ICC beam often becomes the only intermediate step between the ground and the 48″-high floor. The top of the ICC beam usually has traction holes to facilitate this climb. Nonetheless, the two 24″ steps are a daunting climb for anyone. This difficult task is compounded for shorter, older, heavier, or physically-challenged operators.
Similarly, a heavy truck cab floor is typically about 50 inches above the ground, with two steps in-between—i.e., the steps have 17″ risers. By comparison, steps in a home or office usually have 7″ risers, and ladder rungs are usually 12″ apart. This significant height of the steps is one factor that makes truck cabs and trailers difficult to access.
To address this problem, one or more add-on steps can be used. Some existing trailers include a welded or bolted step, tucked forward, above the ICC beam at its center span, or at its far right hand (RH) side, to help facilitate the climb. While helpful, this step does nothing to attenuate the obstacle posed by the first 24″ step. Complicated, multi-link, retractable two-step aids have been on the market for some time. However, these suffer from cost and complexity of product, and of their assembly to the trailer; and any bending of the links, or severe rusting, make them inoperable.
Even with any type of add-on step alone, the climb is difficult because there is generally no standard hand hold or other auxiliary hand hold that can be safely, efficiently and effectively used. As previously noted, a typical step riser in a home or commercial building is 7″ tall. The typical rungs on a ladder are 12″ apart. Both offer continuous hand holds—residential and commercial building steps generally have continuous railings, and the ladder has one rail for each hand. Two points determine a line, about which one can spin out-of-balance. Three non-linear points set a stable plane. As a result, the Society of Automotive Engineers (SAE) recommends in Section 4.7 of SAE J-185 that access systems such as steps, ladders, and grab rails to, on, and from vehicle platforms and walkways, should be designed to allow the person using them to have three points of contact on the system at all times (two hands and one foot, or two feet and one hand). In order to continuously maintain the SAE-recommended “three points of contact” for preventing falls, four points of contact must be provided, as the climb requires the sequential release and raising of each limb. Many cabs and catwalks do not provide two hand holds that extend vertically in proportion to the above climbs. Virtually no trailers do.
On a relatively few existing trailers, hand holds have been added to the right-hand (RH) edge of the cargo box (the RH door opens first in a hinged-door trailer). Even fewer trailers offer a vertical hand hold bolted near the center edge of the left-hand (LH) door. Generally none have both, as their span is about 55″—very hard to use together, similar to executing an “iron-cross” in gymnastics. In either case, their mounting, slightly aft of the rear floor-edge, also forces the climber's center of gravity (CG) back, with the feet further forward—inducing a backward lean, and biasing any slip into becoming a backward fall, often onto hard pavement.
Permanent handles on the door itself would also be out of position when the door is swung open, and if permanently mounted to the floor, would block opening of a trailer's double swinging doors. Some trailers have a garage-type “pull-up” rear door. In that instance, if a permanent hand hold were to be mounted to the outboard side edge of the trailer's rear surface, that would still provide only a single hand hold. Both hands need separate grips to maintain the SAE-recommended three-point contact, as one releases and lifts each limb sequentially during a climb.